“We’re currently on the scene with one ambulance, one helicopter and two PRIME doctors [Primary Response In Medical Emergencies],” a spokeswoman said.
One patient is being assessed at the scene in a moderate condition, St John said, adding that more information will be provided “when it becomes available”.
The police Serious Crash Unit is attending the crash near the Marble Point stock underbridge.
Waka Kotahi has advised road users to avoid the area or delay their journey - and has warned the highway could be closed into the afternoon.
There is no detour available in this area which follows the Waiau River, the transport agency’s maintenance contract manager for North Canterbury, Steve Rusbatch said.
Motorists are advised to delay their travel or use SH1 through Kaikōura to get to Nelson or the Arthur’s Pass route (SH73) if they are travelling between the West Coast/ Buller and Canterbury.